As a biodegradable material from biomass resources, polylactic acid gets rid of the unique dependence on the petroleum resource, and can completely degrade under the action of micro-organism and finally become carbon dioxide and water, therefore it meets the need of environment protection and no any other material can compete with it in consideration of its outstanding low carbon charge, biocompatibility, biodegradability, good mechanical and service performances. However, the defects of the brittle character due to its relatively high glass temperature (about 50-60° C.) and bad heat tolerance due to its low softening point greatly limit the application of a polylactic acid. Therefore, domestic and oversea researchers have carried out massive investigations on the improvement of the toughness and heat tolerance of a polylactic acid.
The toughening of a polylactic acid is carried out mainly by copolymerizing and blending. Copolymerizing has the defects of complicated technology, long production period, high, cost, difficult implementing and continuous industrialized production, while to the contrary, blending is easily realized. Therefore, toughening of a polylactic acid is carried out mainly by blending using the existing device.
A kind of toughening agent is rubber-type elastic materials such as a copolymer of methyl methacrylate-betandiene-styrene used in CN 101875763A, and ethylene copolymer or olefin compounds with epoxy functional group as an impact resistant and toughening modifier used in CN 101495568A, US Pat. Pub. No. 2010/0112357, and US Pat. Pub. No. 2006/0263394, etc.
Moreover, it is preferable to use biodegradable materials as toughening agent of a polylactic acid. For example, US Pat. Pub. No. 2008/0281018 mentions a mixture of biodegradable polyesters comprising an aliphatic-aromatic copolyester A, an aliphatic-aromatic copolyester B, other biodegradable polyesters, and compounds with epoxy functional group, wherein Composites comprising an aliphatic-aromatic copolyester A, an aliphatic-aromatic copolyester B, a polylactic acid, and compounds with epoxy functional group are contained.